
//匀速运动
function doMove( obj, target ,speed ){
	speed = obj.offsetLeft < target ? speed : -speed;

	clearInterval( obj.timer );
	obj.timer = setInterval(function (){
		var nextPos = oDiv.offsetLeft + speed;
		if ( nextPos > target && speed > 0 || nextPos < target && speed <0 ) {
			nextPos = target;
		};

		oDiv.style.left = nextPos + 'px';
		if ( nextPos == target ) {
			clearInterval(obj.timer);
		};
	},30)
}